Abstract 4534: National Multidisciplinary Tumor Board improves diagnostic stratification and therapeutic management in Cancers of Unknown Primary: the French Experience

Abstract Introduction: With the increasing complexity of current diagnostic investigations, the integration of clinical, pathological and molecular characteristics is crucial for the management of patients (pts) with cancers of unknown primary (CUP). A national multidisciplinary tumor board (NatCUPMTB) was created 2 years ago in France to discuss the diagnostic and therapeutic management of CUP pts. The objective of this study was to evaluate its diagnostic, prognostic and therapeutic impact after 2 years of activity. Methods: This was a multicenter retrospective study with prospective follow-up. All pts discussed at least once in the NatCUPMTB between June 2020 and August 2022 were included. Pts and tumors characteristics, pathological and molecular analyses including WGS, WES and RNAseq performed on SEQOIA and AURAGEN national large-scale sequencing platforms, multidisciplinary tumor board (MTB) conclusions, and follow-up after MTB were collected. Results: 76 pts for whom a long-term follow-up was available were included. The median age at diagnosis was 57 yo, 54% were female, and the median number of metastatic sites at diagnosis was 2. The median time between diagnosis and first MTB presentation was 3.8 months (0.2-55). MTB investigations enabled to identify a likely primary origin in 44/76 (58%) pts, and the MTB recommended a personalized therapeutic strategy in 50/76 patients (66%). MTB recommendations were based on the combination of clinical, pathological and molecular investigations in 55% of pts. After a median follow-up of 6.2 months, the median overall survival (OS) was 17.7 months from diagnosis and 11.0 months from the 1st MTB presentation. Pts for which the MTB had a diagnostic impact, and having received a treatment following MTB recommendation (based on putative origin or targetable alteration) had increased OS compared to pts with no diagnostic orientation (median OS 18.4 months vs 5.6 months, p=0.003) or having received other treatments (median OS 18.4 vs 4.4 months, p=0.0001). Conclusion: NatCUPMTB provides significant diagnostic and therapeutic benefit in pts with CUP. Early presentation of pts at NatCUPMTB as soon as CUP diagnosis is suspected should be recommended. Citation Format: Nicolas Jacquin, Maud Kamal, Ivan Bieche, Célia Dupain, Isabelle Guillou, Linda Larbi-Chérif, Etienne Rouleau, Julien Masliah Planchon, Isabelle Soubeyran, Christelle de la Fouchardière, Camille Tlemsani, Hélène Blons, Fabienne Escande, Michel Vidaud, Jennifer Wong, Pierre Saintigny, Sandrine Boyault, Adrien Buisson, Yves Allory, Anne Vincent-Salomon, Vincent Cockenpot, Janick Selves, Christophe Le Tourneau, Sarah Watson. National Multidisciplinary Tumor Board improves diagnostic stratification and therapeutic management in Cancers of Unknown Primary: the French Experience. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4534.